The invention discloses a common-rail oil sprayer. The common-rail oil sprayer is characterized in that a control cavity comprises a control piston, an oil sprayer body and an orifice plate. The common-rail oil sprayer has the advantages that the shape of the bottom of the orifice plate and the shape of the top of the control piston are reasonably designed, so that throttle belts can be formed by the control piston and the bottom of the orifice plate when oil is sprayed by the oil sprayer, throttle effects can be realized, dynamically returned oil of the oil sprayer can be greatly reduced, heat generated by the oil sprayer can be decreased, and power loss of an oil supply pump can be reduced; throttle belt gaps between the bottom of the orifice plate and the head of the control piston are precisely designed, so that the piston is in a completely floating state after being completely lifted up; the throttle belt gaps between the control piston and the bottom of the orifice plate are automatically adjusted in a floating manner by the aid of hydraulic balance, so that pressure difference of the control cavity due to assembly errors and different throttle belt gaps can be reduced, and the assembly consistency of the oil sprayer can be improved.